1. Field of the Invention
The present invention relates to an endoscope in which a metallic lens barrel provided at a distal end rigid portion made of resin and a metallic bending tube are electrically conducted with each other.
2. Description of the Related Art
In recent years, endoscopes to be inserted into a subject have been widely used in medical fields. Observation in a subject is performed with an endoscope by an elongated insertion portion of the endoscope being inserted into the subject. In addition, in general, a rigid member (distal end rigid portion) provided at a distal end of an insertion portion of an endoscope is made of a metal material having conductivity in many cases. In particular, in an endoscope including an insertion portion whose outer diameter is small, a circumference of an image pickup unit is not covered with a metal shield so as to reduce the diameter size of the insertion portion, and a distal end rigid portion is made of metal so as to ensure strength, in many cases.
Therefore, even if static electricity is applied to the distal end rigid portion, the static electricity flows from the distal end rigid portion to the bending tube, and does not leak to the image pickup unit. However, recently, for the purpose of reducing production costs and ensuring voltage endurance in the case where a high-frequency treatment instrument is used with an endoscope, endoscopes including a distal end rigid portion made of resin having an electric insulation property have appeared.
For example, the publication No. WO2012/124526 discloses a technique for preventing a noise from intruding into the image pickup device unit by connecting the metallic connection tube provided at the distal end rigid portion made of resin to the reinforcing barrel provided on the outer circumference of the image pickup device unit, and connecting the reinforcing barrel to the ground portion of the video processor through various kinds of grounding metal members that form a structure of the insertion portion.
In addition, Japanese Patent Application Laid-Open Publication No. 2013-198566 discloses a technique for preventing a noise caused by static electricity, high frequency, or the like from intruding into the image pickup unit, by bringing the channel pipe, which is provided in the distal end rigid portion made of the electric insulation member and grounded, and the device barrel having conductivity of the image pickup unit into surface contact with each other through the conductive member.